Identifying Structural Variations of Thalassemia Using HiFi Sequencing

person receiving a blood transfusion
Thalassemia is a lesser-known genetic blood disorder that affects millions of people worldwide. While it may not be as familiar as other conditions, thalassemia has a significant impact health and well-being. Thalassemia affects the body's ability to produce hemoglobin, a crucial protein found in red blood cells. Hemoglobin is responsible for carrying oxygen from the lungs to the body's tissues and organs.
Thalassemia includes a broad spectrum of phenotypes. This ranges from asymptomatic features to mild or severe anemia. In patients who require blood transfusions, increased iron absorption can further complicate their condition.
This disorder can be categorized in two primary types of thalassemia:
1. Alpha Thalassemia, characterized by problems with the production of alpha-globin chains. These chains are a part of the hemoglobin molecule. The severity of alpha thalassemia can vary, with more severe forms causing significant health issues and necessitating regular blood transfusions.
2. Beta Thalassemia, which involves mutations in the beta-globin genes. It has two main subtypes: the first is Thalassemia Major, a severe form of beta thalassemia. This condition requires frequent blood transfusions to sustain life. Thalassemia Intermedia is a milder form of beta thalassemia. While it may not require transfusions, it can still lead to various health complications.
Thalassemia is a genetic disorder that varies depending on the specific genetic mutations inherited from the parents. There are more than 700 recorded mutations in the alpha-globin gene. Additional insights have been reported thanks to new sequencing technologies. Screening is essential for prenatal diagnosis, genetic counseling, and identification of couples with high risk.
This is especially true of severe forms of the disease that occur in high-frequency areas. Thalassemia has a known geographical distribution, with a high prevalence in Southeast Asia, the Mediterranean, sub-Saharan Africa, the Middle East, and India. It is also widely distributed in northern Europe and North America due to migration of high-risk populations.
Given this geographical specificity and wide variety of mutations, detection of genetic mutations important for screening and diagnosis confirmation. A more complete list of mutations would help healthcare professionals to understand the genetic basis of these disorders and develop more effective treatments.
This is the motivation behind a recent study published by a Chinese team of researchers. In this study, genetic assays and prenatal diagnosis were used to identify a novel 91.5-kb deletion in the alpha-globin gene cluster. This deletion was found to be a rare thalassemia mutation possibly responsible for microcytic hypochromic anemia in the family studied.
Researchers took advantage of PacBio HiFi sequencing. HiFi sequencing is a highly accurate long-read method with no GC bias. PacBio HiFi sequencing has been used previously in analysis of complex genetic diseases like alpha thalassemia. Compared to PCR-based methods, long read sequencing is better suited for the detection of rare and novel genetic mutations.
With this technology, researchers were able to identify a novel mutation not detected by standard genetic assays. These results led researchers to recommend standard genetic testing using short read sequencing for at-risk individuals, plus Single molecule Real-Time (SMRT) for rare mutations. SMRT provides many kilobases of long read sequencing data for the same individual target molecule permitting elucidation of large structural variations impossible with short read technologies. 
This research shows how HiFi sequencing can explain disease phenotypes that were previously unidentified. Common genetic tests were unable to pinpoint this family's genetic mutation. However, with long-read sequencing technology, researchers were able to identify a novel deletion and provide prenatal counseling for one of the study's participants.

Thalassemia is a complex blood disorder with far-reaching implications for those affected by it. Understanding its types, causes, symptoms, and available treatments is crucial for both patients and their families. Early diagnosis, proper medical care, and regular monitoring can greatly improve the quality of life for individuals with thalassemia.
Additionally, genetic counseling and prenatal testing can help individuals with a family history of thalassemia make informed decisions about family planning. Increasing awareness about this condition is essential to support those living with thalassemia and to promote research into more effective treatments and, ultimately, a cure.